1. Field of the Invention
The present invention relates to a display device, and more particularly, to a color filter substrate and fabricating method thereof, an LCD panel, and an LCD device.
2. Description of Related Art
Along with the increasing demand of display devices day by day, manufacturers in this industry have endeavored to improve the quality of display devices. Conventionally, since the cathode ray tube (CRT) is fully developed and has good display quality, the CRT has been adopted in a variety of applications for a long time. However, because of the emerge of environmental concerns, the bulky CRT having high energy consumption, high radiation, and limited flattening capability is gradually unable to meet the market trend that requires a light, thin, short, small and aesthetically pleasing device with low power consumption. Thus, thin film transistor liquid crystal display (TFT LCD) has become the mainstream product in the market due to its superior properties of high definition, high space utilization, low power consumption and no radiation, etc.
The TFT LCD panel is mainly composed of an LCD panel and a backlight module, in which the LCD panel is mainly composed of a thin film transistor array substrate, a color filter substrate, and a liquid crystal layer disposed between the two substrates. In addition, the back light module provides the surface light source required by the LCD panel, so as to achieve the display effect of the TFT LCD.
FIGS. 1A to 1C are schematic cross-sectional views of the conventional fabricating method of the color filter substrate. Referring to FIG. 1A, the conventional fabricating method of the color filter substrate includes the following steps. First, a transparent substrate 110 is provided, and then a black matrix (BM) 120 is formed on the transparent substrate 110. Next, a color filter layer 130 is formed on the transparent substrate 110. Following this, a sputtering process is performed to form a conductive layer 140 on the transparent substrate 110 to cover the color filter layer 130 and the BM 120.
Referring to FIG. 1B, in the multi-domain vertical alignment (MVA) wide viewing angle technology, protrusions or slits are commonly used to make the molecules of liquid crystal generate multi-domain alignment. The fabrication of the slits is generally as follows: a patterned photoresist layer 150 is formed on the conductive layer 140, wherein the photoresist layer 150 has a plurality of slits 150a to partially expose the conductive layer 140. Next, an etching process used for the conductive layer 140 is performed by using the photoresist layer 150 as a mask so as to form a patterned conductive layer 142. Wherein, the patterned conductive layer 142 has a plurality of slits 142a to partially expose the color filter layer 130.
Finally, the patterned photoresist layer 150 is removed to form a structure as shown in FIG. 1C. Thereby, the fabrication of the conventional color filter substrate 100 is initially completed. It should be noted that a side etching phenomenon is often occurred on the patterned conductive layer 142 due to the wet etching process. As a result, the width of the slits 142a of the conductive layer 142 is larger than that of the slits 150a of the patterned photoresist layer 150 (as shown in FIG. 1B), and the difference L1 is the so-called “critical dimension loss” (CD loss). Generally speaking, the CD loss is normally larger than 0.6 micrometer. Nevertheless, as the slits 142a of the patterned conductive layer 142 are developed toward “fine slits”, the size requirement of the CD loss is stricter. Thus, the level of the existing process will become gradually unacceptable.
In addition, since the slits 142a of the patterned conductive layer 142 partially expose the color filter layer 130, moisture or ions can easily penetrate into the color filter layer 130 through the slits 142a. After an LCD panel is assembled, moisture or ions inside the color filter layer 130 are likely to infiltrate into the liquid crystal layer and contaminate liquid crystals. Furthermore, in the etching process of forming the slits 142a, the adhesion between the patterned conductive layer 142 and the color filter layer 130 composed of organic material is weakened due to the impurities such as moisture or ions. As a result, the patterned conductive layer 142 and the color filter layer 130 may easily peel off. Consequently, not only the CD loss of the slits 142a of the patterned conductive layer 142 is relatively large, but the contour of the slits 142a of the patterned conductive layer 142 are also inconsistent and variations of the CD loss are too large. In other words, the slits 142a of the prior art will cause a decrease of the reliability of the conventional color filter substrate 100.
The conductive layer (or the patterned conductive layer) of the TFT array substrate generally serves to generate the electrical field and connect circuits. Therefore, the thickness thereof is required not to be excessively thick. A range between 300 to 500 Å and a surface resistance between 40 to 100 Ohm/square (Ω/□) are generally acceptable.
In addition to forming the electrical field, the conductive layer 140 (or the patterned conductive layer 142) of the color filter substrate should be thick enough to fully cover the color filter layer 130, so that the impurities contained in the color filter layer 130 can be prevented from being released and infiltrating into the liquid crystal layer to contaminate the liquid crystals after the LCD device (not shown) is assembled, and therefore affect the characteristic of the display. The viewing angle of the known vertical alignment LCD can be improved by setting the liquid crystal molecule orientation in the region of each pixel in several different directions. European Patent Publication No. 0884626-A2 discloses a multi-domain vertically aligned LCD, which has a domain adjustable structure for adjusting the liquid crystal molecule orientation. When a voltage is applied, the liquid crystal molecules in the liquid crystal layer align in tilt angles so that the liquid crystal molecule orientation in the regions of each pixel has several directions. In general, the domain adjustable structure is disposed above the conductive layer; therefore, after the LCD is assembled, it is possible that the impurities contained in the domain adjustable structure are released and infiltrate into the liquid crystal layer to contaminate the liquid crystals. Additionally, an organic over coating (OC) layer made of special materials can be used to cover the color filter layer 130 to prevent the impurities from being released from the color filter layer 130 and infiltrating into the liquid crystal layer to contaminate the liquid crystals. However, the material of the organic over coating (OC) layer is rare and expensive, and is controlled by a limited few manufacturers. Furthermore, in order to prevent the conductive layer from being cracked when the spacers formed thereon are pressed, and the material inside the color filter layer being released into the liquid crystal layer contaminating the liquid crystals, and influencing the property of the LCD, the conductive layer 140 should have a sufficient thickness (generally between 1400˜1600 angstrom) to enhance the pressure resistance. The material of the conductive layer 140 of a general transmissive LCD is indium tin oxide (ITO). However, because of excessive pressure onto the surface of the LCD, the ITO under the spacers will crack so as to cause abnormality of cell gaps in the local regions. Consequently, the brightness between the region and other regions is not uniform, thereby affecting the display property.
Moreover, a general TFT LCD utilizes the electrical field between the conductive layer (or the patterned conductive layer) and the color filter substrate to control the liquid crystal layer sandwiched between two substrates. Therefore, if foreign objects/contaminants are present in the two substrates, the disposition of the electrical field will be affected, causing malfunction of the pixels where the foreign objects exist. Ultimately, a constant bright spot or dark spot will be formed, and the viewing quality of the LCD will be affected.